This section is intended to introduce the reader to various aspects of art, which may be associated with embodiments of the present invention. This discussion is believed to be helpful in providing the reader with information to facilitate a better understanding of particular techniques of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not necessarily as admissions of prior art.
Hydrocarbon production from subterranean reservoirs commonly includes a well completed in either a cased-hole or an open-hole condition. In cased-hole applications, a well casing is placed in the well and the annulus between the casing and the well is filled with cement. Perforations are made through the casing and the cement into the production zones to allow formation fluids (such as, hydrocarbons) to flow from the production zones into the conduit within the casing. Additionally or alternatively, the fluid flow may be from the conduit within the casing into the subterranean formation, such as during injection operations. While the discussion herein will generally refer to production operations and fluid flow in the production direction, the principles and technologies described herein apply by analogy to fluid flow in the injection direction. A production string (or, an injection string), consisting primarily of one or more tubulars, is then placed inside the casing, creating an annulus between the casing and the production string. Formation fluids flow into the annulus and then into the production string to the surface through tubulars associated with the production string. In open-hole applications, the production string is directly placed inside the well without casing or cement. Formation fluids flow into the annulus between the formation and the production string and then into the production string to surface.
Modern hydrocarbon wells generally pass through or into multiple subterranean formation types and are continually reaching ever greater depths and/or lengths (such as for extended reach horizontal wells). Additionally, it is common for hydrocarbon wells to extend through multiple reservoirs over the life of the well. In some implementations, the well may extend through multiple reservoirs during any given production operation. Additionally or alternatively, a well may extend though a single reservoir that operates more like multiple reservoirs due to the variations of formation properties within the reservoir and/or the size of the reservoir.
The ever increasing complexity of modern hydrocarbon production operations often necessitates increasingly complex well constructions and completions. The construction of a hydrocarbon well typically includes modeling the subsurface to estimate the formation and reservoir properties. The modeling typically includes inputs from geologic and seismic data as well as data from test wells and/or adjacent wells in the field. These modeling efforts enable the scientists and engineers to identify a preferred location for the well and preferred drilling parameters for the drilling of the well. For example, the rate of penetration, the mud weight, and several parameters related to the drilling operation can affect the long-term operation of the well. While the models and the technology underlying the models are continually evolving, the scientists and engineers are left with an approximation based on previously collected data. The drilling operation is a dynamic, multi-parameter operation where changes in any one parameter could impact any of several parameters over the life of the well.
While the drilling plan can have significant impact on the operation of the well during its life, the completion of the well is often considered determinative of how a given well, once drilled, will operate. As used herein, completion is used generically to refer to procedures and equipment designed to allow a well to be operated safely and efficiently. The point at which the completion process begins may depend on the type and design of well. However, there are many options applied or actions performed during the construction phase of a well that have significant impact on the productivity of the well. Accordingly, completion plans are often prepared prior to the drilling operations based on the models and collected data. The completion plans are often updated based on data collected during the drilling operations to further optimize the operation of the well (whether injection or production).
Despite the accuracy or completeness of the data available when the completion plan is finalized and the completion is implemented in the well, the well's evolution, the reservoir's evolution, and the formation's evolution during the life of the well make most completions inadequate for the extended life of the well. Accordingly, sophisticated work-over procedures have been developed to allow operators to change the completion of a well after production and/or injection operations have begun. Additionally, several efforts have been made to develop intelligent or flexible completions that can be changed during the life of the well without requiring the withdrawal of the completion equipment from the well. Many of these intelligent completions require mechanical equipment downhole that is controlled from the surface between two or more configurations. While the adaptable completion concept is sound, the harsh conditions of the well and the long life of the well generally complicate efforts to manipulate these multi-configuration mechanical devices deep in the well. Moreover, the requirement of these systems to be activated from the surface creates a time delay while the results of the changed downhole condition increasingly manifests itself at the surface and is observed at the surface, and then the control signal can be sent to the downhole equipment that has to transition between configurations.
When producing fluids from subterranean formations, especially poorly consolidated formations or formations weakened by increasing downhole stress due to well excavation and fluids withdrawal, it is possible to produce solid material (for example, sand) along with the formation fluids. This solids production may reduce well productivity, damage subsurface equipment, and add handling cost on the surface. Controlling the production of solids or particles is one example of the objectives of the completion equipment and procedures. Several downhole solid, particularly sand, control methods are currently being practiced by the industry and are shown in FIGS. 1(a), 1(b), 1(c) and 1(d). In FIG. 1(a), the production string or pipe (not shown) typically includes a sand screen or sand control device 1 around its outer periphery, which is placed adjacent to each production zone. The sand screen prevents the flow of sand from the production zone 2 into the production string (not shown) inside the sand screen 1. Slotted or perforated liners can also be utilized as sand screens or sand control devices. FIG. 1(a) is an example of a screen-only completion with no gravel pack present.
One of the most commonly used techniques for controlling sand production is gravel packing in which sand or other particulate matter is deposited around the production string or well screen to create a downhole filter. FIGS. 1(b) and 1(c) are examples of cased-hole and open-hole gravel packs, respectively. FIG. 1(b) illustrates the gravel pack 3 outside the screen 1, the well casing 5 surrounding the gravel pack 3, and cement 8 around the well casing 5. Typically, perforations 7 are shot through the well casing 5 and cement 8 into the production zone 2 of the subterranean formations around the well. FIG. 1(c) illustrates an open-hole gravel pack wherein the well has no casing and the gravel pack material 3 is deposited around the well sand screen 1.
A variation of a gravel pack involves pumping the gravel slurry at pressures high enough so as to exceed the formation fracture pressure (frac pack). FIG. 1(d) is an example of a Frac-Pack. The well screen 1 is surrounded by a gravel pack 3, which is contained by a well casing 5 and cement 8. Perforations 6 in the well casing allow gravel to be distributed outside the well to the desired interval. The number and placement of perforations are chosen to facilitate effective distribution of the gravel packing outside the well casing to the interval that is being treated with the gravel-slurry.
Flow impairment during production from subterranean formations can result in a reduction in well productivity or complete cessation of well production. This loss of functionality may occur for a number of reasons, including but not limited to: 1) migration of fines, shales, or formation sands; 2) inflow or coning of unwanted fluids (such as, water or gas); 3) formation of inorganic or organic scales; 4) creation of emulsions or sludges; 5) accumulation of drilling debris (such as, mud additives and filter cake); 6) excessive inflow of particles, such as sand, into and through the production tubulars due to mechanical damage to sand control screen and/or due to incomplete or ineffective gravel pack implementations; 7) and mechanical failure due to borehole collapse, reservoir compaction/subsidence, or other geomechanical movements.
There are several examples of technology that has been developed in efforts to address these problems. Examples of such technologies can be found in numerous U.S. patents, including those mentioned briefly here. For example, U.S. Pat. No. 6,622,794 discloses a screen equipped with a flow control device, which includes multiple apertures and channels to direct and restrict flow. The fluid flow through the screen is disclosed as being reduced by controlling downhole apertures from the surface between fully opened and completely closed positions. U.S. Pat. No. 6,619,397 discloses a tool for zone isolation and flow control in horizontal wells. The tool is composed of blank base pipes, screens with closeable ports on the base pipe, and conventional screens positioned in an alternating manner. The closeable ports allow complete gravel pack over the blank base pipe section, flow shutoff for zone isolation, and selective flow control. U.S. Pat. No. 5,896,928 discloses a flow control device placed downhole with or without a screen. The device has a labyrinth which provides a tortuous flow path or helical restriction. The level of restriction in each labyrinth is controlled from the surface by adjusting a sliding sleeve so that flow from each perforated zone (for example, water zone, oil zone) can be controlled. U.S. Pat. No. 5,642,781 discloses a well screen jacket composed of overlapped members wherein the openings allow fluid flow through alternate contraction, expansion and provide fluid flow direction change in the well (or multi-passage). Such design may mitigate solids plugging of screen jacket openings by establishing both filtering and fluid flow momentum advantages.
Numerous other examples can be identified. However, current industry well designs and completions plans include little, if any, redundancy in the event of problems or failures resulting in flow impairment. In many instances, the ability of a well to produce at or near its design capacity is sustained by only a “single” barrier to the impairment mechanism (for example, a single screen for ensuring sand control). In many instances, the utility of the well may be compromised by impairment occurring in the single barrier. As indicated above, flow impairment may occur by a variety of mechanisms and various efforts have been made to address these mechanisms, including efforts to provide redundant barriers to the impairment mechanism. However, the systems currently available fail to provide a system that provides redundancy in the prevention of two or more impairment mechanisms. For example, prevention of impairment mechanisms such as particulate inflow and particulate blockages. Therefore, overall system reliability of the presently available systems is low. Accordingly, there is a need for well completion equipment and methods to provide multiple flow pathways inside the well that provides redundant flow pathways in the event of particulate blockage, particulate inflow, or other forms of impairment.